Core B. Mouse Core Project Summary The Mouse Core, Core B, is designed to provide wild-type and mutant mouse testes to the three experimental Projects in this application (Mello, Theurkauf, and Zamore). Cindy Tipping, who will staff the core, is skilled in both genotyping and breeding mice, and she will track investigator's mouse needs using mLIMS, the secure cloud-based colony management tool in current use by the Zamore laboratory. Initially, Ms Tipping will provide freshly dissected testes to the researchers from the Projects in this application. Subsequently, Dr. Zamore, the director of the Mouse Core, will advise members of the individual investigators' laboratories in the regulatory and technical procedures required to work with mice, allowing them to be added to the Zamore laboratory's existing IACUC-approved protocol. Ms Tipping will instruct these researchers in standard mouse methods, including testis dissection. Importantly, the Mouse Core will adopt a barcode system for sample management, develop a LIMS database that will interface with the Bioinformatics Core (Core A), and institute rigorous quality control measures. Investigators will have access to this password-protected data via any web browser. These Core activities will promote integration between the research projects and cores of this Program Project Relevance The services provided by the Mouse Core (Core B) are essential to support the fundamental research proposed by each of the three experimental Projects. The Mouse Core will integrate the Projects in their efforts understand the role of piRNAs in the mammalian testis, promoting the discovery of evolutionarily conserved and mammalian-specific features of the piRNA pathway.